4210 jig & 1/2 box joints

I would postulate that your guide bushing is not exactly centered in your router plate. I had the same problem making 1/4 inch box joints with my PC jig.

If that’s the case you have two options
1. Drift the holes in the plate to center (easier said than done)
2. When cutting, make sure you hold the router in the same “clock” position at all times in addition to holding it to the left side of the template.

-- Joe

Welcome to Lumberjocks! I wish I had the experience to help, but i wanted to welcome you, and assure you there are so many great, helpful folks here, that I’m sure my lack of info won’t be an impediment. Good Luck!

-- -Gerry, Hereford, AZ ” A really good woodworker knows how the hide his / her mistakes.”

Hello . thanks for the welcome gerry and advise joe.

I definitely have it clocked the same. Im going to try again pushing harder to the left and recenter the base too. It looks right but with such small tolerances it would be hard to eye the difference.

Thanks again

I use the alignment cone that comes with the guide bushing set (from Rockler) to check the base alignment. I had to modify the base by counter boring the mounting holes. Don’t understand why Porter Cable would put tapered holes. Maybe someday I’ll buy an after market base that is more accurate, because I haven’t been able to get the centering better than about 0.005.

In a way though it has a good side effect. For example if the joints are too tight you can rout them with the router handles at say 3:00, and then turn them to 3:15 and route again, and voila, the width is slightly increased. Maximum adjustment would result if the clock was adjust to 3:45 (I think).

Good luck

-- Joe

Maybe somebody else can tell you if this idea has any value, but I would check that your router bit is a true .500, and perfectly balanced. If it is larger, or if it is off center, it will be impossible to get the exact .500 cut that you need. Maybe you just need a better quality bit.

I have an alignment thing for my bosch too and it works well, I need to double check the centering but Im pretty sure its as close as I am going to get it.

The bit is .500 for sure, double checked. I never got back to it today so going to give it a whirl tomorrow just by checking center and pressing harder to the left. It may have been drifting and I didn’t notice.